This circuit, from the 70's, can be assembled with a more modern FET like the BF245. The circuit is powered by a 9 V battery, as its consumption is very low.
This circuit is from a 1966 General Electric documentation. The circuit applies to sensitive SCRs for...
In the figure a circuit that is the basic application of NE567 for the detection of a tone applied to...
Found in old documentation, this circuit is the receiver for the previous circuit. Components are...